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From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Roman Gushchin <guro@fb.com>
Cc: linux-mm@kvack.org, Michal Hocko <mhocko@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-kernel@vger.kernel.org, kernel-team@fb.com,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Shakeel Butt <shakeelb@google.com>
Subject: Re: [PATCH] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly
Date: Wed, 30 Oct 2019 17:03:14 -0400	[thread overview]
Message-ID: <20191030210314.2el7wysojucqypoq@ca-dmjordan1.us.oracle.com> (raw)
In-Reply-To: <20191025232710.4081957-1-guro@fb.com>

Hi Roman,

On Fri, Oct 25, 2019 at 04:27:10PM -0700, Roman Gushchin wrote:
> page_cgroup_ino() doesn't return a valid memcg pointer for non-compund
> slab pages, because it depends on PgHead AND PgSlab flags to be set
> to determine the memory cgroup from the kmem_cache.
> It's correct for compound pages, but not for generic small pages. Those
> don't have PgHead set, so it ends up returning zero.
> 
> Fix this by replacing the condition to PageSlab() && !PageTail().

You may also want to update the comment above memcg_from_slab_page():

 * So this function assumes that the page can pass PageHead() and PageSlab()
 * checks.

  parent reply	other threads:[~2019-10-30 21:04 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-25 23:27 [PATCH] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly Roman Gushchin
2019-10-30 19:40 ` Roman Gushchin
2019-10-30 20:40 ` Shakeel Butt
2019-10-30 21:03 ` Daniel Jordan [this message]
2019-10-30 21:35   ` Roman Gushchin

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